Monday, February 17, 2014

It's shocking how much venom and bile you can stir up by criticizing Darwin in public. I more or less expected, when I wrote a post critical of evolutionary theory at BigThink.com, there'd be a few heated comments. I didn't expect so many of the 600+ comments to be so heated. Quite a few of the comments were and are just plain ugly. And the most vitriolic attacks came not from the religious right, but from supporters of Darwin!

Looks like I struck a nerve.

Some people jumped to the conclusion that, with my post, BigThink was selling creationism under a thin veneer of science. That's just plain wrong. I am not a creationist. I consider creationism magical thinking. It may be satisfying to others. It's not for me.

More than one commenter suggested I get some biology training before writing about evolution. I guess I should have made clear, up front, that I have two degrees in biology: a B.S. from UCI and a master's in microbiology (summa cum laude) from UC Davis, where I was a Regents' Fellow. I took (and passed) qualifying exams for a Ph.D. One of the specialty areas I was examined in was molecular genetics.

What did I say in my BigThink blog that was so controversial? First let's get clear what I did not say. One of the commenters claimed I said changes in DNA were not responsible for evolution. I never said that. What I said was that point mutations (of the kind the give rise to single-nucleotide polymorphisms) are almost certainly not a major driver of evolution. We know this because it's been demonstrated many times that the majority of non-neutral point mutations are deleterious, leading to loss of function, not gain of function. Spend some time reading about "Muller's ratchet" if you don't believe me.

How, then, does speciation occur? We don't know. No one has seen it occur in the lab. Nature no doubt relies on a variety of tactics, some of which we know a good deal about, many of which we barely understand, no doubt others of which we haven't yet discovered. We know that sexuality (which is probably around a billion years old) has led to an explosion of diversity (and has kept Muller's ratchet from sending countless species into extinction). On a molecular level, there are still many things we don't understand about how chromatin is managed, how micro-RNA is regulated, when and why DNA methylases come into play, the relative importance (or unimportance) of translocases, and much, much more. To assert that we understand how speciation occurs is to assert a half-truth. It's like saying we understand the weather because we can measure atmospheric pressure.

One of the major embarrassments of modern biology is that more than a decade after having sequenced the human genome, we still don't know what most of our DNA does: We can account for 30,000 human genes (which is not even ten times the number of genes in E. coli). Meanwhile our DNA has enough base-pairs to encode 3 million genes. But we're pretty sure the "true number" of human genes is under 50,000. What does all that DNA do? We have some hints at answers, but no more than that. (Note: When the surplus of DNA in the human genome was first discovered, scientists called it "junk DNA." It took years for that unfortunate terminology to disappear.) The honest answer is, we're still not even close to understanding what all our DNA is doing.

It's been my experience that the best scientists are humble, rather than proud. They're willing to concede the immensity of what they don't know. Arrogance and over-confidence are hallmarks of immaturity, in science as well as in life.

If we're humble, and honest, we have to admit that physics is unable to explain where most of the matter and energy in the universe is. (No one knows what "dark matter" is, where it came from, what its properties are, whether it's made of particles, how long it's been around, whether it obeys normal laws of physics, etc.) If we're humble, we have to admit we don't know what most of the human genome is doing. We also have to admit we don't know how or why the Cambrian Explosion happened. (Darwin himself conceded that the Cambrian Explosion posed a major unanswered challenge to his theory.) We have to admit we have no idea how life originated on earth.

The list of things we don't understand is far longer than the list of things we do understand. If we don't understand that, all is lost.